The present invention is directed to the field of firearms and more particularly involves an automatic/semi-automatic hand-held pistol based on the design of the military M16 rifle.
The M16 automatic rifle and the AR15 semi-automatic rifle have been the standard issue weapons of the U.S. military and civilian police departments for decades. The rifle design was originated by E. M. Stoner and developed by Fairchild Engine and Airplane Company in the 1950's. Modified versions of the M16 designated as the M16A1 and M16A2 are currently in use by armed forces in the U.S. and throughout the world. A civilian semi-automatic version of the M16 designated as the AR15 is sold to civilians by Olympic Arms of Olympia, Wash. When used herein, the phrase "M16" is intended to include all versions of the M16 and AR15 previously and currently being produced.
One of the basic patents on gas-operated firearms was U.S. Pat. No. 2,951,424 issued to E. S. Stoner on Sep. 6, 1960, disclosing the M16 bolt and bolt carrier system and the gas operation thereof. This patent discloses a rifle utilizing a gas tube that extends from gas ports in the barrel, back into the receiver of the rifle and into a gas tube pocket or "key" attached to the bolt carrier.
Other patents which disclose conventional AR15 and M16 designs include U.S. Pat. No. 3,236,155 to Sturtevant issued Feb. 22, 1966, and U.S. Pat. No. 3,742,636 to Dealy et al. issued Jul. 3, 1973.
U.S. Pat. No. 3,675,534, issued to P. C. Beretta on Jul. 11, 1972, discloses a gas-operated automatic rifle having a piston and stem inside a gas tube with the stem fixedly attached to the bolt carrier.
U.S. Pat. No. 4,358,986, issued to C. Giorgio on Nov. 16, 1982, discloses a gas-operated automatic rifle having a stationary piston and a segmented movable gas cylinder/operating rod assembly including a biasing spring.
U.S. Pat. No. 3,618,457, issued to A. Miller on Nov. 9, 1971, and U.S. Pat. No. 3,318,912, issued to Miller on May 9, 1967, both disclose a gas-operated rifle utilizing a gas-operated piston and rod assembly with the piston rod telescopically mounted over a stationary guide rod and being spring-biased.
While the aforementioned patents all disclose various constructions for M16 rifles having gas-operated bolt assemblies, none discloses structure for utilization as a pistol having the M16 type of upper and lower receivers, sliding and rotating bolt assembly, and gas operation.
Also, whereas numerous automatic and semi-automatic pistol designs are known in the art, they utilize a "blowback" design wherein the bolt is not locked up in the chamber when the cartridge is fired. Furthermore, the automatic and semi-automatic pistol designs that are utilized are designed for the relatively mild, low pressure cartridges generally associated with pistols and revolvers, such as the 45 ACP, 9 mm, 38 special, and 357 and 44 magnum calibers. To the best of this inventor's knowledge, no automatic or semi-automatic pistol design has ever been commercialized that is capable of handling the long "bottle-necked" rifle cartridges or of handling the high pressures generated in such rifle cartridges. The pressures normally associated with conventional pistol cartridges generally range from around 30,000 up to about 40,000 CUP (copper units of pressure). This allows for the use of the limited "blow-back" bolt design.
Rifle cartridges, on the other hand, are generally much larger in powder capacity and generate internal pressures in the range of about 50,000 to 60,000 CUP, requiring a locking bolt design. Semi-automatic and automatic pistol designs are incapable of handling rifle cartridges.
In addition, the conventional M16 rifle design does not lend itself to a pistol design for several reasons. One reason is the length of the M16 bolt assembly (bolt and bolt carrier) which requires a long chamber area to the rear of the upper receiver to allow cycling of the bolt assembly backward during the firing cycle. Another reason is the requirement for a buffer tube extending from the rear of the receiver area for containing a buffer and buffer spring which are necessary in the M16 for absorbing the recoil of the bolt and then cycling the bolt forward after a cartridge has been fired.